#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
using namespace std;

const int N = 1e6 + 10, INF = 0x3f3f3f3f;

int n;
map<int, int> hs;

void solve()
{
    cin >> n;
    for (int i = 1;i <= 2 * n;i++) {
        int x;cin >> x;
        hs[x]++;
    }
    int ans = 0;
    for (int i = 1;i <= n;i++) {
        ans += min(hs[i], 2);
    }
    cout << ans;
}

signed main()
{
    //ios::sync_with_stdio(0);
    //cin.tie(0);cout.tie(0);
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    //cin>>T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}